The present invention relates to an ultrasonic diagnosis apparatus and, more particularly, to an improvement of an ultrasonic transducer array used in an ultrasonic diagnosis apparatus.
In general, an ultrasonic wave is transmitted from a transducer array in an ultrasonic diagnosis apparatus to an object to be examined, and the transducer array receives echo signals from tissue of the object, thereby acquiring medical information. A B-mode image (i.e., a tomogram) of the object is most important. It is also often important to measure the flow rate of the blood of a patient for subsequent medical diagnosis. In a conventional method of measuring a blood flow, a frequency shift of echo signals of an ultrasonic wave transmitted from the ultrasonic transducer is detected based on the Doppler effect.
According to a first technique of the conventional blood flow measuring method, a Doppler ultrasonic beam is radiated to an object of interest from one direction, and the flow rate of blood is calculated in accordance with the frequency shift of the reflected ultrasonic beam. According to this technique, when the Doppler beam direction is not perpendicular to the blood flow, the resultant blood velocity VO must be corrected to obtain an actual flow rate V such that V=VO.times.cos (.theta.). For this reason, an angle .theta. formed by the Doppler beam direction and the blood flow direction must be measured on the screen of a TV monitor for displaying an ultrasonic tomogram.
According to a second technique, two ultrasonic probes are used. Two ultrasonic Doppler beams are radiated to the object of interest from two different directions. In this case, a mechanical means is indispensable to measure an angle formed by the two ultrasonic beams at the measuring point. In addition, a mechanical operation is also required to coincide one ultrasonic beam with the other at the measuring point. However, it is very difficult to cross the two Doppler beams on a plane including the measuring point. Since accurate coincidence of the two beams can be performed only with difficulty, blood flow measurement cannot be performed with high precision.